Piston



' I BY Oct, 12, 193 7.

H. B. CHAFFIN 2,095,629

PISTON Filed July 21, 1936 ZSheets-Sheet 1 i It WI NESSES-ZZ 15 lg 15 INVENTOR- a, Z7

mrry B. Chafin,

TORN E YS.

Patented Oct. 12, 1937 UNITED STATES PATENT OFFICE 3 Claims.

This invention relates to pistons and, more particularly to those of the type forming the subjectmatter of my prior Patent No. 2,012,956, dated September 3, 1935; such pistons including a body 5 portion with laterally-spaced circumferential grooves and a combined bull-and-packing ring composed of lapping arcuate segments jointly providing a plurality of laterally-spaced internal ridges adapted to snugly fit the grooves aforesaid,

each said ridge having an inwardly-open groove for reception of appropriate expander means for yieldingly-maintaining the ring segments in fiuidtight contact with a coactive surrounding wall.

In practice, pistons of the type referred to have proven generally satisfactory in providing a fluidtight working-seal with the coactive wall, but it has been discovered that leakage develops between the adjoining end junctures of the combined bull-and-packing ring arcuate segments, and it is the primary aim of this invention to improve such rings so as to positively ensure fluid-tight contact between all of the piston components under all conditions of service. Another object of this invention is to interlock the bull-and-packing ring segments in a manner whereby the normal wear expansion is equally distributed throughout said ring.

A further and more specific object is to provide a novel means whereby the arcuate segment circumferential junctures are positively sealed against leakage while being maintained in fluidtight contact with the surrounding coactive surface.

Other and more specific features of the invention residing in advantageous forms and relations of the improved piston structure, hereinafter described, will later on appear and be tersely expressed in the claims at the conclusion of this specification.

In the accompanying drawings:

Fig. I is a face view of a piston in accordance with the'present invention, parts being broken out, on planes corresponding with the indicated sections a--a and bb in Figs. II and III, to better disclose otherwise hidden features.

Fig. II is a detail cross sectional view on a larger scale, and taken as indicated by the arrows IIII in Figs. I and III.

Fig. III is a fragmentary peripheral view, on a larger scale, than Fig. I, showing the outer sur- I face of the piston in linear development.

Fig. IV is a similar view of a slightly modified form of the invention.

Fig. V is a cross sectional view, taken on the plane designated VV in Fig. IV.

Fig. VI is a view corresponding to Figs. III and IV of a further modified form of the invention; and, 5

Fig. VII is a sectional view on the plane designated by the arrows VII-VII in the preceding illustration.

In all of the views, corresponding parts are distinguished by like characters of reference; with 10 added prime exponents to differentiate the modified structures.

Referring more in detail to the drawings, and to Figs. IIII more particularly, the numeral l comprehensively designates the piston which has a broad peripheral portion 2 integrally formed with a continuous dished web 3, a central boss 4, and a plurality of laterally-spaced circumferential grooves 5, 5, with an intervening central groove 1. These grooves 5, 5 and 'l, are preferably of rectangular-section and of greater depth than width, while it is to be noted the grooves 5, 5 are of corresponding cross-section, whereas the groove 1 is substantially narrower, transversely of the piston l. The piston i, may, obviously, be fabricated as a unit, or it may comprise two or more parts appropriately attached together.

The combined bull-and-packing ring, it will be seen, is composed of a series of interchangeable 0 arcuate segments 8, of a width approximating somewhat that of the piston peripheral portion 2, and has internally thereof a pair of laterallyspaced circumferential ridges 9 of a cross-section to snugly fit in the piston grooves 5, 5, hereinbefore referred to. The circumferential ridges 9 are provided with continuous inwardly-open central grooves l0, preferably of a depth greater than their width, and of a cross-section for free reception of suitable split expander-rings l I, having inner fiat faces l2 for coaction with the bottoms of the piston grooves 5, 5, and their outer edges I3, preferably of half-round section, for engagement with the similarly rounded bottoms of the ridge grooves in, although the rings I I may r be of any other desirable cross section or type, without departure from the spirit of the inven- "tion, to ensure even engagement throughout the circumferential contacting surfaces of the piston grooves 5, 5, and the expander rings H, as well as intermediate the latter and the arcuate segments 8. Oil grooves It are conveniently provided around the combined bull-and-packing ring.

Referring again to the piston groove 1, it is to be noted that the same is located laterally central with and underneath the position occupied by the inner circumferential junctures l5- Fig, IIIof the arcuate segments 8, and said groove is occupied by and substantially filled with a rectangular section outwardly-expanding relatively non-rotative ring l6, which functions to positively maintain a fluid-tight surface contact between its outer periphery I! and the inner face of said segments, along a circumferential plane spanning the junctures l5 aforesaid.

As wear around the outer peripheral surface ll of the combined bull-and-packing ring occurs, relative to the contacting surface of a cylinder wall l9, as shown in Fig. II, an outward radial movement of the arcuate segments 8 proportionately takes place; and, in order to distribute the transverse gap 28, thus developed, as well as prevent said gap from growing at one transverse joint between the confronting ends of a pair of segments 8 only, which gap 28 may exceed the length of the circumferential juncture l5 between adjoining segments 8, there is provided an interlocking circumferential juncture 2|. As best understood from Fig. III. the interlocking circumferential juncture 2! is preferably constituted by providing each segment 8 with an offset or radial step portion 22, the circumferential faces 23 whereof have a fluid-tight working contact with the confronting faces of the respective segments 8, while the inner transverse faces 24 of the stepped portions 22 are sufficiently separated along radial lines, from one another, to insure between any two adjoining segments a circumferential movement not to exceed a comparatively small percentage of the length of any one segment at their circumferential juncture I5.

In the embodiment of the invention shown by Figs. IV and V, like reference characters are employed with the addition of a prime exponent, in order to avoid unnecessary repetitive description. However, it will be seen the structure involved differs somewhat materially from that shown by Figs. I-III, inclusive, in that the piston peripheral portion 2' is provided with three spaced grooves 5', 5 and 5a (in lieu of the plural grooves 5, 5, before described) and a'palr of intervening grooves 1', although any desired odd number of grooves may be utilized according to requirement; while the combined bull-and-packing ring is substantially inset in the piston peripheral portion 2 In addition, the non-rotatable rings l6 are provided on their inner peripheral surfaces with grooves 25 for reception of roundsection split annular expander springs 26, or said rings l6 may be of the snap type or built up with suitable expander means, effective to maintain the rings IS in firm engagement with the underside of the respective circumferential interlocking junctures 2|, afforded by forming the successive arcuate segments 8' with double step portions 22 as will be readily understood, without further explanation herein.

Referring now to Figs. VI and VII, there is shown a further form of the invention, or a combined bull-and-packing ring differing only from the structure of Figs. I to III, inclusive, in that no outwardly-expanding ring I6 is employed below the circumferential interlocking junctures 2|" of the segments 8". In all other respects this form of the invention conforms with that first described, accordingly like reference characters are employed plus the distinguishing exponent double prime, in order to avoid repetitive explanation.

From the foregoing it will be self evident that an advance in the art has been made by the present invention, or in other words there is provided a combined bull-and-packing ring which can be easily applied, that will function with little perceptible wear, one that can be relied upon to effectively overcome the shortcomings of the patented ring hereinbefore referred to, and which positively ensures a fiuid-tight seal during the serviceable life of such packing rings.

Finally, while the invention has been described as preferably adapted to locomotive cylinder pistons, it will be obvious that it is equally applicable to other reciprocatory elements, accordingly the right is reserved to not only employ the structure hereinbefore explained in other connections, but to make such minor changes and variations therein as may be found. necessary for such other usage, and the scope of the following claims permit.

Having thus described my invention, I claim:

1. In a piston having spaced peripheral grooves, and a combined bull-and-packing ring composed of lapping arcuate segments having internal ridges engageable in said grooves with intervening expander means to uniformly urge the ring outwardly into fluidtight contact with a surrounding wall, step portions on the circumfer-. entially-directed lapping faces of the arcuate segment ends, the inner confronting edges whereof are spaced to define radial gaps. a circumferential groove in the piston peripheral portion below the circumferential juncture of the arcu ate segments, and a non-rotative ring fitting in the last mentioned groove spanning the juncture aforesaid and adapted to positively seal said juncture against leakage while maintaining the ring segments in fluid-tight contact with a surrounding coactive wall.

2. The combination of claim 1, wherein the piston circumferentialgroove is of rectangular cross-section, and the 'non-rotative ring is split and expandingly fits into said groove, for the purpose specified.

3. The combination of claim 1 wherein the piston periphery has plural grooves with intervening non-wearing material ring receiving grooves, the combined bull-and-packing ring segments have complemental ridges engageable in the plural grooves, and the non-rotative rings have inwardly open grooves for reception of suitable expander elements, ior the purpose specified.

HARRY B. CI-IAFFIN. 

